Filtration units are typically employed in liquid, e.g., water, waste, etc., treatment plants for purifying the liquid. This involves filtering particles, e.g., micron, submicron, etc., from the liquid to produce a filtered liquid (or filtrate). Many filtration units use bundles of hollow-fiber membranes, e.g., small diameter tubes having permeable walls, for filtering. In some applications, the bundles are immersed in the liquid to be filtered and filtrate passes through the permeable walls and into the tubes under a pressure gradient. One problem with using bundles of hollow-fiber membranes is that hollow-fiber membranes are expensive.
Some filtration units use a number of sheet membrane modules for filtering. Typically, each sheet membrane module includes a pair of sheet membranes separated by a flow passage. The sheet membrane modules are usually immersed in the liquid to be filtered and filtrate passes through the pair of sheet membranes of each sheet membrane module and into the flow passage under a pressure gradient. Most of these filtration units are constructed by potting several of sheet membranes within a container using, for example, a liquefied thermoplastic, such as polyurethane. However, this is expensive owing to the large amounts of potting material that is typically required.
For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative filtration devices.